Perhaps the right question would be, what are your goals?
If your goals are to have 18s on your truck because you like the aesthetics and don't want to be bothered by the hassle of buying an extra set of wheels or something I can understand, I had that conversation with myself once too.
When you look at your options I would encourage you to look at accessorizing your vehicle in terms of what is practical for preparation or prevention, not in terms of looks.
The saying "everything you need, nothing you don't" or the philosophy of "keep it simple" has everything to do with application and practicality when things get tough.
I think you'd be hard pressed to find an experienced driver choosing 18in wheels for many practical reasons. Weight, room, that is a lot of alloy, tire options, and cost. That doesn't mean you can't do it but, that doesn't mean you should either right?
18s are inherently more difficult to change due to the size. They are much harder to get a tire on the rim and to get a wheel off the truck. If you've never had to change a flat on the trail or rather in conditions less than ideal; mud, sand, rain, water, etc well every advantage helps. 18s weigh more so if you're carrying more than one spare tire they are a lot heavier with off road tires than 16s, they are a lot taller on the roof rack which won't help mpgs or weight distribution etc basically you're giving up quite a bit to have 18s
On the other hand, if you're doing club rides or occasional light treks, life is short and you are entitled to live it your way! But 18s crack easier, and shearing off alloy is bound to happen because there is less height on most 18s. But it can be done and has been done -
let us know what you decide and post some pics and or opinions. Don't let anyone here decide for you, make your decision and find out for yourself
Personal note -
I had 18s on my 04 HSE and they held up great in deep snow but were loud and cost mpgs and I'd never do any serious off road endeavors with them. We are about to purchase ( next few months as prices continue to drop ) a 04 HSE7 or SE7 even though I know energy prices are going to go up again. I think Defenders will become more and more available but I'm not dropping $20K on a 25 year old 110 when I can get a 04 Disco for $6-8K with 50K miles. I fully plan on selling the 18s and getting 16s and I've never seen a Defender of any kind with 18s if that says anything.
Good luck!